Pension plans - Projected benefit obligation, plan assets and net funded status (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
BHE Pension Plan [Member]
Benefit obligations
Accumulated benefit obligation at end of year	$ 4,797	$ 5,105
PBO at beginning of year	5,398	5,006
Service cost	57	60
Interest cost	200	226
Benefits paid	(316)	(310)
Actuarial (gains) or losses and other	(263)	416
PBO at end of year	5,076	5,398	$ 5,006
Plan assets
Plan assets at beginning of year	5,086	4,888
Employer contributions	90	126
Benefits paid	(316)	(310)
Actual return on plan assets	31	525
Other	(126)	(143)
Plan assets at end of year	4,765	5,086	4,888
Funded status - net liability	311	312
All Other Pension Plans [Member]
Benefit obligations
Accumulated benefit obligation at end of year	9,264	9,522
PBO at beginning of year	10,489	8,892
Service cost	209	170
Interest cost	391	403
Benefits paid	(518)	(524)
Business acquisitions	165	11
Actuarial (gains) or losses and other	(553)	1,537
PBO at end of year	10,183	10,489	8,892
Plan assets
Plan assets at beginning of year	8,280	8,389
Employer contributions	116	122
Benefits paid	(518)	(524)
Actual return on plan assets	80	338
Business acquisitions	167	1
Other	(59)	(46)
Plan assets at end of year	8,066	8,280	8,389
Funded status - net liability	2,117	2,209
Pension Plans, Defined Benefit [Member]
Benefit obligations
Accumulated benefit obligation at end of year	14,061	14,627
PBO at beginning of year	15,887	13,898
Service cost	266	230	254
Interest cost	591	629	547
Benefits paid	(834)	(834)
Business acquisitions	165	11
Actuarial (gains) or losses and other	(816)	1,953
PBO at end of year	15,259	15,887	13,898
Plan assets
Plan assets at beginning of year	13,366	13,277
Employer contributions	206	248
Benefits paid	(834)	(834)
Actual return on plan assets	111	863
Business acquisitions	167	1
Other	(185)	(189)
Plan assets at end of year	12,831	13,366	$ 13,277
Funded status - net liability	$ 2,428	$ 2,521